Iain is correct. Short of the Leica Monochrom you can’t shoot B&W RAW. I’m fairly sure that is the only camera set permanently to the equivalent of B&W film.

The B&W image you see on the camera monitor is a small processed JPEG file. When you open the RAW you need to re-process it. Like sharpness, colour and all those other settings, if you shoot RAW they are irrelevant.

If your camera has the option, you can set it to ‘RAW+JPEG’ which will capture the RAW file for you and also save a full size JPEG processed to B&W (if you set the camera to B&W).

As far as I know, shooting RAW capture everything the sensor captures. And since your sensor is a color sensor the camera will always have color RAW files. Any black and white treatment is a processed photo therefore not RAW. I’m not 100% familiar with Canons, but I would think you can shoot RAW+JPEG to get the color RAW and the B&W JPEG which you can use as a reference point for when you convert your RAW. Or, if you really want B&W RAWs, Leica has a model that just shoots B&W. There might be others, but I don’t know for sure.